Clamp and reinforcing ring for pipe wrapping

ABSTRACT

A clamping and reinforcing ring for a pipe wrapped with high strength metal strapping. The clamping and reinforcing ring comprises a unitary metal annulus which is fitted over the wrapped pipe, and having a concave inner surface in the central portion of the annulus. When the wrapped pipe is expanded in the radial direction, the concave portion of the annulus is deformed to increase the radius of curvature and thereby produce a spring force pressing radially inwardly on the wrapped pipe. One or both peripheral portions of the annulus are bent outwardly away from the surface of the wrapped pipe to facilitate fitting of the ring over the wrapped pipe.

Fencl CLAMP AND REINFORCING RING FOR PIPE WRAPPING Mar. 19, 1974 PrimaryExaminerJerry W. Myracle Attorney, Agent, or FirmWolfe, Hubbard, Leydig.Voit & Osann, Ltd,

[75] Inventor: Vernon R. Fencl, Northbrook, ML

[73] Assignee: Grotnes Machine Works, Inc.,

Chicago In [57] ABSTRACT [22] Filed: Feb 22, 1972 A clamping andreinforcing ring for a pipe wrapped with high strength metal strapping.The clamping and PP 2271797 reinforcing ring comprises a unitary metalannulus which is fitted over the wrapped pipe, and having a [5 2] US.Cl. 138/147 concave inner Surface in the Central portion of the [51] HF16! 9/04 nulus. When the wrapped pipe is expanded in the ra- [58] Fieldof Search 138/109, 150, 147; dial direction, the 0mm: Porno" Of theannulus 285 397 4 7 4 2 deformed IO increase the radius Of curvature and5 6; 292/256 2 7/9 4 3 5; thereby pl'OdLlCC a spring force pressingradially inwardly on the wrapped pipe. One or both peripheral [56]References Cited portions of the annulus arebent outwardly away fromUNITED STATES PATENTS the surface of the wrapped pipe to fac1l1tatefitting of the ring over the wrapped pipe. 435,927 9/1890 Ginty 285/417X 3 Claims, 4 Drawing Figures CLAMP AND REINFORCING RING FOR PIPEWRAPPING The present invention relates generally to pipes wrapped withreinforcing material such as metal strapping or the like and, moreparticularly, to an improved method and apparatus for the clamping andreinforcing of such wrapped pipe.

It is a primary object of this invention to provide an improved methodand apparatus for clamping and reinforcing a wrapped pipe by means of asingle unitary metal ring which produces a positive spring forcepressing radially inwardly on the wrapped pipe.

It is another object of the invention to provide an improved apparatusof the foregoing type that is simple and economical to fabricate, andwhich can be assembled by only a few quick, simple operations.

A further object of the invention is to provide such an improved methodand apparatus that provides a clamping pressure substantially greaterthan that effected by a clamp formed by a simple flat band of metal.

Other objects and advantages of the present invention will becomeapparent from the following detailed description, taken in conjunctionwith the attached drawings, in which:

FIG. 1 is a perspective view of a pipe wrapped with metal strapping anda clamping and reinforcing ring ready to be applied to the wrapped pipe;

FIG. 2 is an enlarged section through a fragment of one wall of thewrapped pipe of FIG. 1 with the clamping and reinforcing ring applied;

FIG. 3 is a side elevation of the end portions of two sections ofwrapped pipe welded together, with each pipe section carrying a clampingand reinforcing ring as shown in FIGS. 1 and 2; and v FIG. 4 is anenlarged section through fragments of the welded walls of the pipesections shown in FIG. 3.

While the invention will be described hereinafter in connection with asingle illustrated embodiment, it is to be understood that the intent isnot to limit it to that embodiment. To the contrary, the intent is tocover all alternatives, modifications and equivalents falling within thespirit and scope of the invention as defined by the appended claims.

Turning now to the drawings, and referring first to FIGS. 1 and 2, thereis shown a pipe having multiple layers l1, 12, 13 and 14 of highstrength metal strapping wound around it. The metal strapping reinforcesthe pipe 10 to reduce the likelihood of fractures in the pipe, and alsoprevents propagation of a fracture along the length of the pipe if andwhen a fracture occurs. Each of the layers 11, 12, 13 and 14 of metalstrapping is formed by a single strip of strapping wrapped around thepipe 10 in a helical pattern, with the edges of adjacent windings ofeach helical wrapping abutting each other to form a substantiallycontinuous cylindrical wrapping around the pipe. Wrappings of the typeillustrated are especially useful on metal pipes of relatively largediameter of the type used, for example, in gas pipe lines; fractures insuch pipe lines have been known to propagate over distances as long asseveral miles when pipe that was not wrapped was used, resulting insubstantial economic losses. Wrapped pipe of the type illustrated may beformed by the method and apparatus described in the assignees copendingapplication, Ser.

No. 227,822, entitled Method and Apparatus For Wrapping Pipe WithMultiple Strips of Strapping filed concurrently herewith.

To form pipe lines, successive lengths of the pipe illustrated in FIGS.1 and 2 are typically joined by welding. Thus, in FIGS. 3 and 4 twosections of wrapped pipe 10 and 10a are butted against each other andwelded together as at 15. The heat from the welding operation may weakenthe pipe somewhat in the area adjacent the weld, and for this reasonfractures are more likely to occur near the ends of the individuallengths of pipe that make up the pipe line. I

In accordance with the present invention, the end portion of the ,pipeand the wrapping thereon are clamped and reinforced by a unitary metalring or annulus having at least one annular portion forming a concaveinner surface spaced away from the peripheries of the annulus, with theannulus being radially expanded to produce a spring force pressingradially inwardly on the wrapped pipe. Thus in the illustrativearrangement, a clamping ring 20 comprises a unitary metal annulusforming a pair of annular peripheral sections 21 and 22 and an annularcenter section 23 curved outwardly away from the wrapped pipe to form aconcave inner surface 24. The ring engages the surface of the wrappedpipe on both sides of the concave surface 24 so that when the pipe 10 isexpanded in the radial direction, the center section 23 of the ring isdeformed to increase the radius of the curvature thereof, therebycreating a spring force pressing inwardly against the wrapped pipe inthe radial direction. That is, the radial expansion of the wrapped pipedeforms the bowed center section 23 from its original configuration, andthe tendency of the deformed center section 23 to return to its originalconfiguration produces a radial biasing force applied inwardly againstthe wrapped pipe.

The radial expansion of the wrapped pipe 10 to deform the clamping ring20, and thereby achieve the desired clamping action, may be effected bya conventional expanding mandrel, such as the one described in US. Pat.No. 3,583,200 to Cvijanovic. The expanding mandrel expands the pipe byapplying outward radial forces to the inside wall of the pipe around theentire circumference thereof. When the mandrel is collapsed to removethe expansion forces, the wrapped pipe and the clamping ring both tendto spring back to some degree, and it is important that the clampingring have a greater radial spring back than the wrappedpipe for theparticular expansion effected in any given application so as to maintainthe desired spring force on the wrapped pipe. It is also important thatthe wrapped pipe retain at least a portion of the radial expansioneffected by the expanding mandrel, so that the curved center section 23of the clamping ring remains deformed to some extent to maintain thedesired biasing force on the wrapped pipe.

In pipe lines for carrying natural gas or other fluids, the fluidpressure inside the pipe often expands the pipe radially outwardly,particularly near the ends of welded pipe sections where the strength ofthe pipe may have been reduced somewhat by the heat from the weldingoperation. In this connection, a further advantage of the ring 20 isthat any such radial expansion of the pipe in the field simply deformsthe concave center section 23 of the ring to automatically increase thereinforcing force applied by the ring 20. To insure that the ring 20provides this automatic reinforcing function in the field, it isimportant that the initial deformation of the cancave ring section 23,when the pipe is first expanded by an expanding mandrel, be such thatthe ring section 23 retains a concave inner surface. That is, theinitial expansion of the wrapped pipe by the expanding mandrel shoulddeform the ring to increase the radius of curvature of the centersection 23, but it should not completely flatten the ring so that it nolonger has a concave inner surface when the pipe is used in the field.

In accordance with one particular aspect of the invention, at least theperiphery of the clamping ring that is located farther away from the endof the wrapped pipe is flared outwardly away from the pipe to facilitatefitting of the ring over the wrapped pipe. Thus, both peripheralsections 21 and 22 of the illustrative ring are bent outwardly away fromthe wrapped pipe at a light angle so that the inside diameter of theperipheries of the ring are greater than the outside diameter of thewrapped pipe, thereby facilitating the fitting of the ring onto the endof the pipe. The flared periphery also facilitates sliding of theclamping ring 20 axially over the surface of the wrapped pipe withoutcatching on the edges of the successive windings of the outermost layerof metal strapping. Although both peripheral sections 21 and 22 areflared outwardly in the illustrative ring in order to provide asymmetrical structure that can be 4 quickly shipped onto the wrappedpipe without regard to which end of the ring is facing the pipe, it willbe understood that only one end of the ring 20 may be bent outwardly ifdesired.

I claim as my invention:

1. A pipe wrapped with high strength metal strapping and having aclamping and reinforcing ring fitted over the wrapped pipe, said ringcomprising a unitary metal annulus having at least one annular portionforming a concave inner surface spaced away from the peripheries of theannulus whereby radial expansion of said annulus deforms said annularportion to produce a spring force acting inwardly in the radialdirection, both peripheries of said annulus being bent outwardly in theradial direction, and said annulus having a' greater radial spring backthan the wrapped pipe over which the annulus is fitted in response to apredetermined radial expansion so that the annulus maintains a springforce on the wrapped pipe after a radial expansion of both the pipe andthe annulus.

2. The combination of claim 1 wherein said clamping and reinforcing ringis positioned adjacent one end of the wrapped pipe.

3. The combination of claim 1 wherein said wrapped pipe has two clampingand reinforcing rings fitted thereover, said rings being positionedadjacent the ends of the wrapped pipe.

1. A pipe wrapped with high strength metal strapping and having aclamping and reinforcing ring fitted over the wrapped pipe, said ringcomprising a unitary metal annulus having at least one annular portionforming a concave inner surface spaced away from the peripheries of theannulus whereby radial expansion of said annulus deforms said annularportion to produce a spring force acting inwardly in the radialdirection, both peripheries of said annulus being bent outwardly in theradial direction, and said annulus having a greater radial spring backthan the wrapped pipe over which the annulus is fitted in response to apredetermined radial expansion so that the annulus maintains a springforce on the wrapped pipe after a radial expansion of both the pipe andthe annulus.
 2. The combination of claim 1 wherein said clamping andreinforcing ring is positioned adjacent one end of the wrapped pipe. 3.The combination of claim 1 wherein said wrapped pipe has two clampingand reinforcing rings fitted thereover, said rings being positionedadjacent the ends of the wrapped pipe.